R5 is an assessment procedure for the high temperature response of structures and R5 Volume 7 specifies the creep crack growth assessment for low alloy welds.

For high temperature low alloy butt welds, the effects of the welding residual stresses on the creep crack growth for a circumferential defect has been investigated by Shi under a constant temperature of 532.7°C.

In addition to the welding residual stresses, it is well known that temperatures also affect significantly creep deformation, creep rupture and accordingly creep crack growth. Hence, in this paper an investigation for the effects of temperature changes on the creep crack growth and also on component remnant lives has been carried out.

In this paper, for a typical low alloy butt weld in ½Cr½Mo¼V (‘½CMV’) pipework with 2¼Cr weld metal under a given internal pressure and a bending welding residual stress of 60MPa, a series of creep crack growth analyses have been conducted using the R5 Volume 7 assessment procedure, assuming different operating temperatures during different operating periods. A postulated internal circumferential defect (semi-elliptical surface-breaking surface defect) of 2.3 mm deep by 15 mm long has been used.

The investigation results are presented by a series of graphs which show the effects of the temperature changes on the creep crack growth and plant remnant lives for the weld studied. After a detailed discussion, conclusions can be drawn.

This content is only available via PDF.
You do not currently have access to this content.